Breathing apparatus



.i'an. 19, 1960 r A. M. MAYO BREATHING APPARATUS Filed April 1. 1955 iis 0/ 2 Sheets-Sheet 1 4 3 mvsmon ALFRED M. M Y0 Jan. 19, 1960 A. M.MAYO BREATHING APPARATUS Filed April 1, 1955 2 Sheets-Sheet 2 N v Q I b6Miss iQRbbh United States PatentO BREATHING APPARATUS Alfred M. Mayo,Palos Verdes Estates, Calif.

Application April 1, 1955, Serial No. 498,593 6 Claims. (Cl. 137-44 Thisinvention relates to'irnprovements in breathing apparatus of the demandtype.

Breathing apparatus of the demand type operate on the principle ofsupplying breathing fluid, such as air or oxygen or a mixture of air andoxygen, during the inhalation phase in the cycle of breathing andexhausting used or foul fluid during the exhalation phase. This isusually accomplished by apparatus including inhalation and exhalationdiaphragms subject to pressure dilferentials between the respirationpressure and the ambient pressure. The exhalation diaphragm operatesresponsively to relatively high respiration pressure created during theexhalatio'n phase of the breathing cycle for exhausting foul breathingfluid expired from the lungs. Generally, the inhalation diaphragm formsa wall of a pressure or respiration chamber communicating with thetracheal passage of the person being served and is constructed to movein accordance with suction created during the in halation phase foroperating a valve device which co'ntrols the flow of breathing fluidfrom a relatively high pressure source into the chamber and hence to thelungs. Due to the short period of the breathing cycle and the shortinterval of the inhalation phase of each cycle, it is necessary toprovide an apparatus capable of responding quickly to extremely smallpressure difierentials, such as a pressure less than one inch of Water,and supplying a volume of breathing fluid during the inhalation phase,in accordance with the demand of the person being served, in order topermit natural breathing under pressure without requiring expendituresof more than normal breathingefforts. Breathing apparatus provided byprior art, although capable of responding fairly quickly to smallpressure differentials, require the development of a measurable forcefor operating the valve device which controls the flow of breathingfluid into the pressure chamber. Since the operating force for the valvedevice is derived from the suction developed during the inhalationphase, it presents resistance to breathing.

Generally the valve device comprises an orifice connecting therespiration chamber and the source of relatively high pressure breathingfluid, and a valve member positioned for cooperation with the orifice tocontrol the flow of fluid therethrough. The valve member is located onthe high pressure side of the orifice to utilize the relatively highpressure of the source of breathing fluid for holding the valve memberin closed position. In order that the valve member may open responsivelyto slight pressure differentials on the inhalation diaphragm, thediaphragm and the valve member are operatively connected through a forcemultiplying arrangement as provided by a tilt valve assembly, forexample. In such an assembly the valve member is in the form of a discjoined to one end of a valve stem of small cross-sectional area ascompared to the diameter of the orifice. The valve stem passes throughthe orifice and into the respiration chamber with its other end inoperative relation with the inhalation diaphragm. The valve stem isdisposed at an 2,921,594 Patented Jan. 19, 1960 oblique angle withrespect to the plane of the inhalation diaphragm so that the valvemember tilts about one side of the orifice and moves away fromadiametrically opposite side upon movement of the diaphragm responsivelyto suction developed during the inhalation phase. For uniform dependableoperation of this type of valve device it is necessary to provide meansfor concentrically positioning the valve stem and the valve member withrespect to the orifice when the valve member is in closed position. Theprior arrangements employ spring means for accomplishing this centeringfunction which inherently increases the force required for moving thevalve member from the closed position. Since there exists a limit to thedegree of force amplification obtainable, due to the practical size ofthe breathing apparatus and the required flow characteristics of theorifice, for example, the force required to overcome the action of thecentering spring means before the valve member moves from the closedposition, increases-the breathing effort.

Conventional breathing apparatus of the above type do not provide avolume of breathing fluid during the inhalation phase of the breathingcycle in accordance with the actual demand of the individual beingserved, and are not capable of providing natural breathing without theexpenditure of an abnormal breathing effort or Without employing anextremely large diaphragm which results the breathing cycle. The forcerequired to initially move' the valve device from its closed position,including the force required to overcome the resistance offered by thevalve member centering means, prevents establishment of a trueproportional relationship between the suction and the degree of valveopening. Also, the volume of breathing fluid introduced into therespiration chamber during the inhalation phase is adverselydispro'portional to the degree of suction developed. This results fromcertain inherent characteristics of the demand type of breathingapparatus in addition to the .resistance that must be overcome toinitially move the valve apparatus from its closed position. Thepressure drop due to friction in the passageway between the valveapparatus and tracheal passage of the person being served, and theefiect upon the suction acting on the inhalation diaphragm by the streamof breathing fluid introduced into the respiration chamber, are probablypredominant factors efiecting this result.

In the case of artificial breathing under water in which a pressurizeddiving suit is not employed, commonly known as skin diving furtherproblems are presented. In addition to the requirement of a breathingapparatus of light weight, compact and sturdy construction designed forrelatively easy manufacture at low cost, the high density of waterpresents problems not present when breathing in fluids of relativelylighter density, such as atmospheric or subatmospheric air. As mentionedabove, breathing apparatus of the demand type generally includeinhalation and exhalation diaphragms operative responsively to slightpressure differentials for controlling the flow of breathing fluid tothe tracheal passage during the inhalation phase, and exhausting foul orused breathing fluid during the exhalation phase, respectively. Due tothe relatively great density of water, in order to prevent a materialincrease in the breathing effort, the inhalation and exhalationdiaphragms must operate at substantially the same pressure diiferential.If a pressure difiere'ntial exists between the operating pressures ofthe diaphragm, a proportionally greater breathing effort will berequired to permit natural breathing.

It is therefore an object of the present invention to provide abreathing apparatus capable of permitting natural breathing underpressure without the need of ex-' pending more thannormal breathingefforts.

Another object is to provide a novel breathing apparatus in which thevolume of breathing fluid supplied to the tracheal passage of the personbeing served during theinhalation phase of the breathing cycle is inaccordance with the persons actual demand.

Another object is to provide a novel breathing apparatus in which thevolume of breathing fluid introduced into the respiration chamber duringthe inhalation phase of a breathing cycle is not directly proportionalto the degree of suction acting on the inhalation diaphragm.

Another. object is to provide a novel breathing apparatus of the demandtype in which a volume of breathing fluid is introduced into therespiration chamber during the exhalation phase of a breathing cycle inexcess of a volume of breathing fluid proportional to the degreeofsuction acting on the inhalation diaphragm, to supply a volume ofbreathing fluid to the tracheal passage in accordance with the actualdemand of the person being served.

Another object is to provide a breathing apparatus including a novelvalve assembly for controlling the flow of breathing fluid into therespiration chamber which is self-centering and does not require anadditional breathing effort toeffect the centering operation.

Other objects and features of the present invention will appear morefully from the following detailed description considered in connectionwith the accompanying drawings which disclose one embodiment of theinvention. It is to be expressly understood that the drawings aredesigned for purposes of illustration only and not as a definition ofthe limits of the invention, reference for the latter purpose being badto the appended claims.

In the drawings, in which similar reference characters denote similarelements throughout the several views:

Fig. 1 is an elevational view of a breathing apparatus oonstructedinaccordance with the principles of the present invention;

Fig. 2 is a view in section taken along the line 2-2 of Fig. 1;

Fig. 3 is a view in section taken along the line' 3--3 of Fig. 1;

Fig. 4 is an enlarged fragmentary view in section of w a valve deviceshown in Fig. 2, the valve device being illustrated in closed position;

Fig. 5 is an enlarged fragmentary view in section of the valve deviceshown in Fig. 2, the valve device being illustrated in one phase of itsopen position;

Fig. 6 is an enlarged fragmentary view in section of the valve deviceshown in Fig. 2, the valve device being illustrated in another phase ofits open position;

Fig. 7 is an isometric view of aportion of the breathing apparatus shownin Figs. 2 and 3 illustrating a principle of operation employed by thepresent invention, and

Fig. 8 is a diagram illustrating the suction-flow characteristic of abreathing apparatus constructed in accordance with principles of thepresent invention.

In general the present invention provides a breathing apparatus of thedemand type including a respiration chamber having an outlet adapted forcommunication with a person to be served and an inlet communicating withthe respiration chamber through an orifice controlled by a valve deviceand adapted to be connected to a source of breathing fluid underrelatively high pressure. An inhalation diaphragm and an exhalationdiaphragm are provided forming opposed walls of the respiration chamberand are adapted to move responsively to differential variations inpressure within and Without the chamber. The inhalation diaphragmoperates a tilt valve device of a two-stage type which controls the flowof fluid from the inlet through the orifice, while the inhalationdiaphragm controls valve means for exhausting used or foul gas from therespiration chamber to without the breathing apparatus. An arrangementis also provided for reducing the pressure within the respirationchamber responsively to the flow of a stream of breathing fluid thereto.The latter arrangement and the twostage tilt valve device, whilefunctioning independently to effect a supply of breathing fluid inaccordance with the actual demand of the individual beingserved, combineto produce a performance which enables the person being served toexperience natural hreathing'cycles under pressure without the need forthe expenditure of more than normal breathing efiorts.

As shown in Figs. 1, 2 and-3 of thedrawings a breathing apparatus 10constructed in accordance with the principles of the present inventioncomprises a main hollow casing 11 of substantially cylindrical formadapted to support an inhalation diaphragm 12 forming one of its wallsand an exhalation diaphragm 13 forming another wall.

indiametric. relation with theinhalation diaphragm. The casing-11andthediaphragms 12 and 13 define a respiration. chamber 14having a.fluid outlet 15 formed by. a cylindrical extension 16 from one side ofthe casipg 11,

and a fluidinlet 17 of a valve assembly 18 positionedinv an oppositeside. of the casing. The fluid outlet 15 is adapted tov be connected tothe tracheal passageof the personbeing served, by means of aflexibleconduit and a.

breathing mask, .for example, and functions as a passageway forbreathingfluid on its way to the tracheal passage. as well as forconducting to therespiration chamberused or foul fluidexpelled from thelungsduringthe exhalation phase of: the breathing .cycle.

a sourceof. breathing fluid .under relatively high. pressure.

The breathing fluid may comprise atmospheric air, oxy

gen,.or atmospheric air enriched with oxygen stored under relativelyhigh. superatmospheric pressure: in a container. designed for suchpurposes;

mergesinto an enlarged annular portion 27 supported by the annularshoulder 23. The enlarged portion may be formed to fit snugly againstthe fillet portion 25 and the" adjacent portion of the inner surface 20.The enlarged annular portion 27 extends rearwardly a short distance awayfrom the annular shoulder 23 andterminates in an enlarged annular bead29 of circular cross section. The inhalation diaphragm is maintained inthe position shown in the drawings by means of circular cover member30joined to the cylindrical flange 20 by a circumferential bead 31projecting from the edge of the cover member and adapted to enter acomplementary circumferential groove 32 provided in the cylindricalflange-adjacent its outer edge. The circular cover plate includes aninwardly projecting annular flange portion 33 which merges into anoutwardly extending annular flange portion 34 spaced from the coverplate a distance corresponding to the cross-sectional diameter of theannular head 29. The external surfaces ofthe annular flange portion 34which are parallel to the annular shoulder 23 and the inner surface 22are proportionedto snugly contact corresponding inside surfaces of theenlarged portion '27.

The cover plate 30 is also provided withplurality' of openings 35, onlyone of which is shown in the drawings;

The inlet 17 includes: a threadedbore 19 adaptedforforming a' connectionwith.

portable.

to that external pressure may be applied to the outside surface of thediaphragm 12.

The exhalation diaphragm 13 is also constructed of flexible material,such as rubber, and includes a main body member 36 of circularconfiguration merging into an angularly disposed inwardly projectingperipheral valve member 37. The exhalation diaphragm is supported on thecasing by a centrally disposed member 38 extending from the main bodymember and tightly mounted in an opening 39 provided in a central hub 40joined to the casing 11 by a plurality of coplanar radial members 41spaced from each other to provide openings 42. The outer periphery ofthe openings 42 lie on a circle within a circle defined by theperipheral edge of the valve member 37, while the plane of the outersurface of the radial supporting members 41 extends radially outwardlybeyond the circle defined by the peripheral edge of the valve member 37to present a cylindrical valve seat 43 adapted for cooperation with thevalve member. The casing 11 includes a cylindrical flange portion 44extending outwardly from the cylindrical valve surface 43and providedwith an internal circumferential groove 45 adapted to receive acomplementary circumferential bead 46 formed on the edge of a coverplate 47 which overlies the outer edge of the cylindrical flange 44. I,The cover plate 47 is provided with a plurality of openings 48 so thatthe exhalation diaphragm is subject to the pressure surrounding thebreathing apparatus and to allow substantially unimpeded exhaust of usedbreathing gas during the exhalation phase of the breathing cycle. Theexhalation diaphragm is constructed and so positioned in the casing sothat the valve member 37 is in gas-tight contact with the valve seat 43to block fluid flow through the openings 42 whenever the externalpressure exceeds the pressure within the chamber 14. However, thepresence of a relatively high pressure in the respiration chamber causesthe periphery of the valve member to flex upwardly for exhausting thechamber. The diaphragm may be positively mounted on the casing by meansof annular fillets 49 extending outwardly from the circular supportingportion '48 to contact either or both side surfaces of the hub portion40.

A hollow member 50 of frusto conical shape is positioned in therespiration chamber 14 in concentric relation with the inhalationdiaphragm 12. The large diameter end of the conical member is supportedon the casing adjacent the enlarged annular portion 27 of the diaphragmby means of an outwardly extending flange 51 adapted to lie in anannular recess 52 formed in the annular flange 21. The conical member 50functions as a support for the inhalation diaphragm to limit inwardmovement of the'diaphragm and thus prevent injury to the diaphragm inthe event an abnormally relatively high pressure exists externally ofthe breathing apparatus. As described more fully below, the conicalmember also functions as means for reducing the pressure of the fluidacting against the inhalation diaphragm during the inhalation phase ofthe breathing cycle. For this reason the conical member extends agreater distance away from the periphery of the inhalation diaphragmthan would be necessary to merely support the inhalation diaphragm, andterminates adjacent the chamber side of the radial supporting members41.

The valve assembly 18 includes a cylindrical housing 55 having anenlarged end portion 56 presenting an external surface 57 adapted tosnugly fit into a suitable opening 58 provided in the casing 11. Ifdesired the surface 57 may be kn urled. The inlet passageway 17 extendsinwardly beyond the threaded bore 19 to form a high pressure chamber 59defined by a transverse partition wall 60. An orifice 61 is centrallyformed in the partition wall 60 to provide a fluid communication betweenthe inlet 17 and the chamber 14. Fluid flow through the orifice 61 iscontrolled by a disc valve 62 located in the high pressure chamber 59.The disc valve 62 is of the tilt type and is connected to one end of avalve stem 63 which passes through the orifice 61 into the chamber 14with its other end 64 extending into abutting relation with the bearingplate 26 of the inhalation diaphragm 12. A suitable filter member 65 maybe provided in the inlet passageway 17.

The valve stem 63 is mounted at an oblique angle with respect to theplane of the inhalation diaphragm 12 and the valve assembly isconstructed so that inward and outward movements of the diaphragm areconverted into tilting movements of the valve member 62. Since the valvestem 63 is in concentric relation with the orifice 61 when the valvemember 62 is in closed position as described below, the valve assembly18 is mounted in the casing 11 at an oblique angle with respect to thediaphragm 12.

Details of the construction of the valve assembly 18 and the manner inwhich the valve 62 controls the flow of fluid from the inlet 17 to thechamber 14 are more fully understood with reference to Figs. 4, 5 and 6of the drawings. As shown, the orifice 61 includes a discharge opening66 on the chamber side of the partition wall 60 and is provided with araised circumferential valve seat 67 on the inlet side. The disc valve62 includes a valve face 68 lying in a plane perpendicular to thelongitudinal axis of the valve stem 63, and the valve face is recessedto carry an annular ring 69 of resilient material, such as rubber,adapted to contact the valve seat throughout its periphery upon the discvalve being urged into contact with the valve seat and concentricallypositioned with respect to the orifice 61, as shown in Fig. 4. The discvalve 62 is urged into this position responsively to the high pressurefluid in the chamber 59 acting on the surface of the disc valve oppositethe valve face 68. In order to position the disc valve in concentricrelation with the orifice 61,

the disc valve is provided with a concentric conical portion 70extending outwardly from the valve face 68 in a direction toward thechamber 14. The diameter of the conical portion 70 at its base adjacentthe valve face is such as to snugly fit within the valve seat 67. Withthis arrangement, the disc valve is automatically centered with respectto the orifice upon its movement in a direction toward the chamber 14.

The valve face 68 of the disc valve 62 is of a diameter substantiallygreater than the diameter of the valve seat 67 and when the disc valve62 is in closed position as shown in Fig. 4, the periphery of the valveface 68 extends radially outwardly from the valve seat in spacedrelation With surface 71 on the inlet side of the partition wall 60.When the end 64 of the valve stem 63 moves to the right, as viewed inFig. 2 of the drawings, upon inward movement of the inhalation diaphragm12, the disc valve 62 tilts away from one side of the valve seat about adiametrically opposite point of the valve seat. This action is shown inFig. 5. Upon further movement of the valve stem 63, the disc valvecontinues to tilt about a point of the valve seat until a peripheralpoint 72 of the valve face 68 contacts the surface 71 of the partitionwall 60, and thereafter upon continued movement of the valve stem thedisc valve tilts with respect to the valve seat about the peripheralpoint- 72 as a fulcrum. This phase of the valve operation is shown inFig. 6. Inasmuch as the periphery of the valve face 68 is displaced agreater radial distance than the valve seat from the longitudinal axisof the valve stem, it is apparent the .disc valve will move a greaterdegree away from the valve seat for a given increment of movement of thevalve. stem when its fulcrum point comprises a peripheral point of thevalve face 68.

As mentioned above, one of the objects of the present invention is toprovide a novel breathing apparatus operable to provide a source ofbreathing fluid in accordance with the actual demand of'a person beingserved controlling the pressure in the respiration chamber 14responsively to the flow of a stream of breathing fluid thereto, and bythe use of a two-stage valve operable responsively to a predetermineddegree of' movement of the inhalation diaphragm to increase the rate offlow of breathing fluid fed to the respiration chamber upon a givenincrement of movement of the inhalation diaphragm. While these featurescombine to provide a breathing apparatus which permits natural breathingunder pressure without expending abnormal breathing efforts, they arealso individually effective in supplying breathing fluid in accordancewith the actual demand of the person being served throughout a widerange of breathing cycles.

The arrangement provided by the present invention for control-ling thepressure in the respiration chamber responsively to the flow of a streamof breathing fluid into the chamber comprises the provision of a fluidstream diflusion member or plate 75 positioned in the respirationchamber 14 in spaced relation with the discharge opening 66 of theorifice 61 and in the path of the stream of fluid introduced into thechamber. The diffusion member 75 is stationary relative to the dischargeopening 66 and lies in a plane substantially perpendicular to thelongitudinal axis of the orifice 61 for effecting maximum diffusion ofthe stream of fluid with a concomitant pressure drop in the respirationchamber in accordance with the rate of flow and velocity of the fluidstream. Inasmuch as the diffusion member 75 is positioned in therespiration chamber in front of the discharge opening 66, the diffusionmember is provided coming stream of breathing fluid in such a manner asto reduce the pressure within the respiration chamber, and comprises abattle which prevents the incoming stream ofbreathing fluid fromimpinging upon the inhalation diaphragm and provides a substantiallyisolated passageway through the respiration chamber to maintain thefluid afiecting inhalation diaphragm movements in a quiescent stateunaffected by turbulence due to the incoming stream. In addition, theuse of the conical member 50 offersadvantages in simplicity ofconstruction and lends to the-use of a control valve of the tilt type.

The manner in which the portion 75 of the conical member 50 diffuses thestream of breathing fluid entering the respiration chamber 14 isillustrated in Fig. 7 of the drawings. The stream of fluid entering therespiration chamber impinges on the diffusion member 75 with the resultthat the fluid stream is diffused into a plurality of thin streams 78,or a thin sheet of fluid, moving along the external surface of themember 75. The bending of the fluid stream during the process of itsdiffusion produces a pressure reduction which effects movement of fluidfrom within the conical member by aspiration and increases the suctionacting on the inhalation diaphragm.

The curve shown in Fig; 8 illustrates the suction-flow characteristic ofa breathing apparatus constructed in accordance with the principles ofthe present invention. This curve was obtained by connecting a source offluid at 40 pounds per square inch pressure to the inlet 17 and with anelongated slot 76 for the passage of the valve stem 63 therethrough. Theslot 76 preferably has a width dimension no greater than necessary forallowing unrestricted tilting movement of the valve stem.

In accordance with another feature of the present invention, the portionof the conical member 50 in the region of the orifice 61 is employed asthe diffusion member 75. As shown in the drawings, the conical member 50extends substantially completely transversely of the respiration chamberand terminates in close proximity with the inside surface of the radialmembers 41. Although the conical member is shown constructed of fluidimpervious material, it is to be expressly understood other structuresmay be employed. For example, the inhalation diaphragm may be supportedby an open framework extending outwardly into the respiration chamber asuflicient distance to support the diaphragm and including a portion offluid impervious material in the region of the discharge opening of theorifice presenting a sufficient area to provide the required diffusion.Also, the provision of a baflle member extending around at least theinlet side of the inhalation diaphragm and in spaced relation wvith thewalls of the respiration chamber, as provided by the conical member 50,presents an arrangement which prevents fluttering of the inhalationdiaphragm due to turbulence in the respiration chamber upon theintroduction of a high velocity stream of breathing fluid thereto.

The passageways formed between the adjacent spaced surfaces of theconical member and the internal walls of the housing 11 aresubstantially isolated from the fluid within the respiration chamberaffecting movement of the inhalation diaphragm and function to maintaina quiescent volume of fluid to affect the diaphragm while conducting thebreathing fluid through the respiration chamber from its inlet to itsoutlet. Thus the use of a conical member 50, as shown in the drawing notonly functions to support the inhalation diaphragm when subject toabnormal pressuredifierentials, but also diffuses the ina vacuum pump tothe outlet passageway 15, and by operating the vacuum pump to subjectthe breathing appara-' tus to predetermined rates'of flow measured inliters per minute. The suction values were obtained by measuring" thepressure in the, outlet passageway 15 for the different ratesof flow.According to this curve the rate of flow and the suction follow asubstantially linear relationship from zero flow and suction to a point80 corresponding to a suction value of approximately 1.1 inches of waterand a rate of flow of approximately 30 liters per minute. At point 80the linear relationship ceases and thereafter the flow increases at agreater rate than the suction until point 81 is reached where thesuction is approximately 1.2 inches of water and the flow approximately40 liters per minute. From point 81 to point 82 the rate offlowincreases, although the suction falls off to approximately 0.9 inchof water, and in the remaining portion 83 of the curve from a point'84the suction and flow follow a substantially linear relationship.

The portion of the curve between points 80. and 84 which displaces thelinear portion from the portion 83,

is produced due to the combined effect of diffusion of:

a suction in excess of two inches of water to provide a flow of litersper minute and the flow would drop oil? at high rates due to choking ofthe input orifice. The latter disadvantage is not present in a breathingapparatus provided by the present invention due to the action of thetwo-stage tilt valve in automatically increasing the size of theoriiicefor a given increment'of inward movement of the inhalation diaphragmduring the range of high rates of flow. Thus the orifice does not chokeat high rates of flow and the apparatus is capable of supplying a volumeof breathing gas to meet the actual demand of the person being servedeven in the case of abnormal or gasping breathing cycles requiring thesupply of: a large volume of breathing fluid within a relatively shortperiod. i

The principles of the present invention described above will be morefully understood by considering the operation of a breathing apparatusduring a breathing cycle. For convenience, the breathing cycle will beconsidered as initiating with the beginning of the exhalation phase.Upon exhalation of a person being served, the foul or used breathingfluid expelled from the lungs is conducted through the mask and flexibleconduit, discussed above, and enters the passageway 15 increasing thepressure in the respiration chamber 14 and hence the pressure acting onthe inside surface of the valve portion 37 of the exhalation diaphragm13. When the pressure in the chamber'14 builds up to a value in excessof theexternal pressure, the valve portion 37 flexes outwardly from thevalve surface 43 exhausting foul breathing fluid from the breathingapparatus. At the end of the exhalation phase the chamber 14 containsfoul breathing fluid at a pressure slightly below the external pressureas determined by the force required to open the exhalation valve.Expansion of the lungs of the person being served at the beginning ofthe inhalation phase produces a source of suction which is transmittedthrough the passageway 15 to the respiration chamber 14. This actionresults in the person receiving the foul breathing fluid remaining inthe respiration chamber at the end of the inhalation phase; however,this is not disadvantageous since breathing regulators embodying theprinciple of the present invention may include respiration chambers ofrelatively small volume and the small quantity of carbon dioxide presenthas a stimulating effect. When the pressure in the resipration chamberis reduced to a value below the external pressure, the inhalationdiaphragm 12 moves inwardly and tilts the valve 62 away from the valveseat 67 allowing the flow of high pressure breathing fluid into thechamber. It is preferable to design the inhalation diaphragm 12 topossess a normal tendency to move inwardly of the chamber and exert apressure through the tilt valve arrangement,

of a sufficient magnitude to balance the force exerted on the open faceof the valve member 62 by the high pressure fluid in the chamber 59.With this arrangement high sensitivity may be obtained so that breathingfluid is introduced into the respiration chamber whenever the pressurein the chamber drops slightly below the external pressure. Upon anincrease in suction in the chamber 14 as the inhalation phase proceeds,the inhalation diaphragm 12 moves further inwardly of the chamberincreasing the size of the opening to the orifice 61. Initially, therate of flow into the respiration chamber is directly proportional tothe suction moving the inhalation diaphragm, however as the rate of flowincreases the pressure in the chamber is reduced due to the aspirationeifect resulting from diffusion of the stream when it impinges on theplate 75. This results in an increase in the rate of flow without aproportional increase in suction. As the suction further increases thevalve member 62 moves to its second stage of opening in which a greaterrate of flow results upon a given increment of inward movement of thediaphragm.

The provision of means for producing an aspiration eifect responsivelyto diffusion of the incoming stream and of a two stage valve forincreasing the rate of flow for a given increment of inward movement ofthe inhalation diaphragm during high rates of flow, allows theconstruction of a compact breathing apparatus including a respirationchamber of relatively small volume and an inhalation diaphragm ofrelatively small area which is operable to supply the proper volume ofbreathing fluid during the inhalation phase of the breathing cycle asdetermined by the demand of the person being served without requiringabnormal breathing effort. The diffusion feature for increasing the rateof flow of the breathing fluid into the respiration chamber without aproportional increase in suction not only tends to negative a reductionin suction due to the discharge of the breathing fluid into therespiration chamber and to compensate for the suction required toinitially rock the tilt valve from its closed position, but, togetherwith the two-stage valve feature, insures the supply of the propervolume of breathing fluid during the inhalation phase of a naturalbreathing cycle. Also, the provision of the diffusion member 75 in thepath of the fluid stream entering the respiration chamber not onlyeffects a reduction of pressure in the chamber by producing anaspiration effect but also prevents the incoming stream from adverselyalfecting normal operation of the inhalation diaphragm. This action isparticularly manifest in the use of the conical member 50, constructedof fluid impervious material, as a support for the diaphragm as well asa diffusion means. In this case the inhalation diaphragm is surroundedby a continuous shield which prevents the incoming fluid from impingingupon the inhalation diaphragm and restricts the inhalation diaphragm toinfluence by a quiescent volume of fluid free from turbulence occasionedby the breathing fluid stream.

The conical member 70, which centers the valve 62 when moved to closedposition, does not increase the force required for opening the valve.Thus a breathing apparatus including valve centering means of thischaracter will respond more rapidly to lower pressure dilferentials andaid in obtaining natural breathing cycles.

As mentioned above, the present invention also provides a breathingapparatus particularly adapted for serving a person who may besurrounded by a fluid of a relatively great density, as in the case ofskin diving; the breathing apparatus being characterized in that little,if any, pressure differential exists between the operating pressures ofthe inhalation and exhalation diaphragms. As shown in Fig. 2, theinhalation and exhalation diaphragms 12 and 13 form opposite walls ofthe respiration chamber 14 and are subject to the same externalpressure. This arrangement establishes a condition in which there existssubstantially no ditferential between the pressure at which theexhalation diaphragm closes and the pressure at which the inhalationdiaphragm opens. The importance of this feature will be more fullyunderstood by consider-ing a condition in which the exhalation diaphragmis mounted on the body of the person being served at a point above theinhalation diaphragm. With these relative locations, the exhalationdiaphragm would close at a pressure below the pressure at which theinhalation diaphragm opens as determined by the difference in fluid headbetween the diaphragms. In the case of skin diving," due to the highdensity of water, only a slight difference in elevation of theinhalation and exhalation diaphragms will result in a substantialpressure differential between their operating pressures adverselyalfecting thev breath-ing effort required. Should the exhalationdiaphragm close at a relatively low pressure, the inhala tion diaphragmwould necessarily possess low sensitivity to prevent premature openingof the inlet valve. Thus a higher degree of suction, equivalent to thepressure differential, would be required to open the inhalationdiaphragm. According to the present invention these difiiculties areeliminated by forming the inhalation and exhalation diaphragms asdiametrically opposed walls of the respiration chamber. This arrangementprevents the development of a material pressure differential between theoperating pressures of the diaphragms irrespective of the location ofthe breathing apparatus with respect to the body of the person beingserved.

While the various components of the breathing apparatus described abovemay be constructed of any suitable material in order to provide acompact apparatus capable of long life that may be manufactured at arelatively low cost, it is preferable to form the casing 11 and thecover plates 30 and 47 of plastic material, such as molded nylon. Suchmaterial possesses excellent anti-corrosion characteristics, especiallyin salt water, and may be easily fabricated into the necessary form toprovide a compact breathing apparatus of lightweight. Also, with moldednylon the casing 11 may be made to possess sulficient resilientcharacteristics so that the cover members may be's'upported' and sealedin the casing 11 bynormal inward deflection of the cooperating walls ofthe casing. The other components of the breathing apparatus may beconstructed of molded plastic material, while it is preferable tomachine the valveassembly'18 from metallic stock to obtain the requiredaccuracy of the orifice 61, the valve seat 67 and the'means forautomatically centering the disc valve 62.

There is thus provided by the present invention a novel breathingapparatus of light-Weight, compact construction capable of longdependable operation and which may be manufactured at relatively lowcost. The 'breathing'appa-- ratus includes novel features which actalone and in combination to supply a volume of breathing fluid duringthe inhalation phase in accordance with the actual demand of the personbeing served to enable the person to breathe naturally Without exertingmore than normal reathing efforts even though the breathing apparatus isof compact construction including an inhalation diaphragm of small areaand a respiration chamber of small volume as compared to conventionaldesigns. The breathing apparatus described above also includes a novelarrangement for reducing to a minimum the force required to initiallyopen the valve device which controls the flow of breathing fluid.Moreover, the present'invention provides a breathing apparatusparticularly adapted for skin diving inwhich the inhalation andexhalation diaphragms operate at substantially the same pressure toprovide high sensitivity.

Although only one embodiment of the present invention has been disclosedand described above, it isto be.

expressly understood that various changes and substitutions may be madeWithout departing from the spirit of the invention as well understood bythose skilled in the art. Reference therefore Will be had to theappended claims for a definition of the limits of the invention.

What is claimed is:

1. A breathing apparatus comprising a hollow casing including a curvedinner Wall defining an opening, a flexible diaphragm positioned in theopeningand secured to the casing so that the casing and the diaphragmform a chamber, the casing having a fluid inlet adapted to be connectedto a source of fluid under pressure and a fluid outlet in communicationwith the chamber, a longitudinally curved diffusion plate located in thechamber with a curved edge thereof in contiguous relation with thecurved inner Wall of the casing adjacent the opening, the curveddiffusion plate extending in a direction away from the opening in spacedoverlying relation with a portion of the inner Wall of the casing, meansforming an orifice between the fluid inlet and the chamber, the orificebeing located in said portion of the inner wall of the casing insubstantial symmetrical relation with the longitudinal dimension of thecurved diilusion plate and the orifice having a discharge opening on itschamber side for discharging a stream of fluid into the chamber and ontothe diffusion plate, valve means operatively associated with the orificefor controlling the flow of fluid' through the discharge opening intothe chamber, the flexible diaphragm being movable responsively todifferential variations in pressure Within and without the chamber, andmeans responsive to movement of the diaphragm for controlling the valvemeans.

2. A breathing apparatus comprising a'hol-lo'w casing to be connected toa source of fluid under pressure and a fluid outlet in communicationwith the chamber, thefie'xible diaphragm being movable to withinthechamber responsively to differential variations in pressure withinand without the chamber, a hollow conical member supported in thechamber in symmetrical relation with respect to the diaphragm and inspaced overlying relation with respect to the inner Wall of the casingwith its large diameter end in contiguous relation with the curved innerwall adjacent the opening to form a support for the diaphragm uponmovement of the diaphragm into the chamber, means forming an orificebetween the fluid inlet and the' chamber, the orifice having a dischargeopening on its chamber side for discharging a stream of fluid into thechamber, valve means operatively associated with the orifice forcontrolling the flow of fluid through the discharge opening into thechamber, and means responsive to movement of the diaphragm forcontrolling the valve means, the hollow conical member including aportion formed of fluid impervious material overlying in spaced relationthe orifice and a portion of the inner Wall surrounding the orifice andbeing substantially symmetrically positioned with respect to the path ofthe stream of fluid discharged from the orifice.

3. A breathing apparatus comprising a hollow casing including a curvedinner wall defining a circular opening, a flexible diaphragm positionedin the opening and secured to the casing so that the casing and thediaphragm form a chamber, the casing having a fluid inlet adapted to beconnected toa source of fluid under pressure and a fluid outlet incommunication with the chamber, the flexible diaphragm being movable towithin the chamber responsively to differential variations in pressurewithin and without the chamber, a hollow conical member formed of fluidimpervious material supported in the chamber in symmetrical'rel'ationwith the diaphragm and with the large diameter end of the hollow conicalmemher in contiguous relation with the curved inner Wall ofthecasing'adjacent the opening to form a support for the diaphragm uponmovement of the diaphragm into the chamber, aportion of the hollowconical member being in spaced overlying relation with a portion of theinner Wall of the casing, means forming an orifice between the fluidinlet and the chamber, the orifice having a discharge opening on itschamber side for discharging a stream of fluid to the chamber, valvemeans operatively associated with the orifice for controlling the flowof fluid through the discharge opening into the chamber, and meansresponsive to movement of the diaphragm for controlling the valvemeans,the orifice being located in said portion of 'the inner Wall of thecasing in substantial symmetrical relation with the longitudinaldimension of said portion of the'hollow conical member so that thestream of fluid discharged from the orifice into the chamber impingesupon said portion of the hollow conical member.

'4. A breathing apparatus comprising a hollow casing including a curvedinner wall defining an opening, a flexible diaphragm positioned in theopening and secured to the casing so that the casing and the diaphragmform achamber, the casing having a fluid inlet adapted to be connectedto a source of fluid under pressure and a fluid: outlet in communicationwith the chamber, a longitudinally curved diflusion plate supported inthe chamber with a curved edge thereof in contiguous relation with thecurved inner wall of the casing adjacent the opening, thecurveddiffusion plate extending in a direction awag from the opening in spacedoverlying relation with a portion of the inner wall of the casing, meansformingan' orifice between the fluid inlet and the chamber, the orificebeing located in said portion of the inner wall of the casing insubstantial symmetrical relation with the longitudinal dimension of thecurved diffusion plate and the orifice having a discharge opening on itschamber side for discharging a stream of fluid pressure into the chamherand onto the difiusion plate, valve means operatively associated withthe orifice for controlling the flow of'fluid through the'dischargeopening into the chamber,

chamber, a valve stem positioned in the chamber and having one endsecured to the valve means and its other end operatively associated withthe diaphragm for controlling the valve means responsively to movementof the diaphragm, and means forming an opening in the longitudinallycurved diffusion plate for passage of the valve stem therethrough.

5. A breathing apparatus comprising a hollow casing including a curvedinner wall defining a circular opening, a flexible diaphragm positionedin the opening and secured to the casing so that the casing and thediaphragm form a chamber, the casing having a fluid inlet adapted to beconnected to a source of fluid under pressure and a fluid outlet incommunication with the chamber, the flexible diaphragm being movable towithin the chamber responsively to differential variations in pressurewithin and without the chamber, a hollow conical member supported in thechamber in symmetrical relation with the diaphragm and in spacedoverlying relation with the inner wall of the casing with its largediameter end in contiguous relation with the curved inner wall adjacentthe opening to form a support for the diaphragm upon movement of thediaphragm into the chamber, means forming an orifice between the fluidinlet and the chamber, the orifice having a discharge opening on itschamber side for discharging a stream of fluid into the chamber, valvemeans operatively associated with the orifice for controlling the flowof fluid through the discharge opening into the chamber, and a valvestem located in the chamber having one end secured to the valve meansand the other end in operative relationship with the diaphragm so thatmovements of the diaphragm control the valve means, the hollow conicalmember including a portion formed of fluid impervious material overlyingin spaced relation the orifice and a portion of the inner wallsurrounding the orifice and being substantially symmetrically positionedwith respect to the path of the stream of fluid discharged from theorifice, the portion of the hollow conical member formed of fluidimpervious material having an opening therein for passage of the valvestem therethrough.

6. A breathing apparatus comprising a hollow casing including a curvedinner wall defining a circular opening, a flexible diaphragm positionedin the opening and secured to the casing so that the casing and thediaphragm form a chamber, the casing having a fluid inlet adapted to beconnected to a source of fluid under pressure and a fluid outlet incommunication with the chamber, the flexible diaphragm being movable towithin the chamber responsively to differential variations in pressurewithin and without the chamber, a hollow conical member formed of fluidimpervious material supported in the chamber in symmetrical relationwith the diaphragm and with its large diameter end in contiguousrelation with the curved inner wall adjacent the opening to form asupport for the diaphragm upon movement of the diaphragm into thechamber, a portion of the hollow conical member being in spacedoverlying relation with a portion of the inner wall of the casing, meansforming an orifice between the fluid inlet and the chamber, the orificehaving a discharge opening on its chamber side for discharging a streamof fluid into the chamber, valve means operatively associated with theorifice for controlling the flow of fluid through the discharge openinginto the chamber, a valve stem located in the chamber 'having one end secured to the valve means and another end in operative relation with thediaphragm so that movements of the diaphragm control the valve means,the orifice being located in said portion of the inner wall of thecasing in substantial symmetrical relationship with the longitudinaldimension of said portion of the hollow conical member so that thestream of fluid discharged from the orifice impinges upon said portionof the hollow conical member, and said portion of the hollow conicalmember having an opening for the passage of the valve stem therethrough.

References Cited in the file of this patent UNITED STATES PATENTS2,399,054 Meidenbauer Apr. 23, 1946 2,436,522 Meidenbauer Feb. 24, 19482,445,359 Meidenbauer July 20, 1948 2,452,670 Meidenbauer Nov. 2, 19482,579,855 Pockel Dec. 25, 1951 2,635,691 Filliung Apr. 21, 19532,728,340 Meidenbauer Dec. 27, 1955 2,766,752 Meidenbauer Oct. 16, 19562,774,352 Emerson Dec. 18, 1956

